Nikkei 225 is a stock market index for the Tokyo Stock Exchange (TSE). It has been calculated daily by the Nihon Keizai Shimbun (Nikkei) newspaper since 1950. It is a price-weighted average (the unit is yen), and the components are reviewed once a year. Currently, the Nikkei is the most widely quoted average of Japanese equities, similar to the Dow Jones Industrial Average. In fact, it was known as the "Nikkei Dow Jones Stock Average" from 1975 to 1985.

The Nikkei 225 began to be calculated on September 7, 1950, retroactively calculated back to May 16, 1949.

The Nikkei 225 Futures, introduced at Singapore Exchange (SGX) in 1986, the Osaka Securities Exchange (OSE) in 1988, Chicago Mercantile Exchange (CME) in 1990, is now an internationally recognized futures index.

The Nikkei average hit its all-time high on December 29, 1989 when it reached an intra-day high of 38,957.44 before closing at 38,915.87. Its high for the 21st century stands just above 18,300 points.

Another major index for the Tokyo Stock Exchange is the Topix.

Links:

http://www.google.com/finance?q=INDEXNIKKEI:.N225

http://www.nni.nikkei.co.jp/e/fr/freetop.aspx

http://en.wikipedia.org/wiki/Nikkei_225